Review on Enhance Your Vehicle's Performance with the Dorman 600-105 4WD Actuator for Ford / Lincoln Models by Michael Radhakrishnan

It worked. If you hear a grinding noise in the front hubs, then either one of those actuators is blown (so it's not holding a seal), or the solenoid is burned, or the insanely stupid vacuum hose Ford put on their F150 (fragile, expensive, sucks and NOT "Ford" Strong") broke. I replaced the flimsy vacuum hose with a regular vacuum hose and routed it through the rear firewall. Added two of these. Presto! Expensive labor much cheaper with quality Dorman parts. Exact OEM compliance Pre-lubricated and all.